To satisfy demands for wireless data traffic having increased since commercialization of 4th-Generation (4G) communication systems, efforts have been made to develop improved 5th-Generation (5G) communication systems or pre-5G communication systems. For this reason, the 5G communication system or the pre-5G communication system is also called a beyond-4G-network communication system or a post-Long Term Evolution (LTE) system.
To achieve a high data rate, implementation of the 5G communication system in an ultra-high frequency (mmWave) band (e.g., a 60 GHz band) is under consideration. In the 5G communication system, beamforming, massive multi-input multi-output (MIMO), full dimensional MIMO (FD-MIMO), an array antenna, analog beamforming, and large-scale antenna technologies have been discussed to alleviate a propagation path loss and to increase a propagation distance in the ultra-high frequency band.
For system network improvement, in the 5G communication system, techniques such as an evolved small cell, an advanced small cell, a cloud radio access network (RAN), an ultra-dense network, a device to device (D2D) communication, a wireless backhaul, a moving network, cooperative communication, coordinated multi-points (CoMPs), and interference cancellation have been developed.
In the 5G system, advanced coding modulation (ACM) schemes including hybrid frequency-shift keying (FSK) and quadrature amplitude modulation (QAM) modulation (FQAM) and sliding window superposition coding (SWSC), and advanced access schemes including filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) have been developed.
User devices such as mobile phones, tablet computers, laptop computers, etc., may be connected to various networks. For example, for use of the Internet, a mobile phone may be connected to a network that is set up in a coffee shop or to a network that is provided for free in a library. An Internet protocol (IP) subnet in case of the connection of the mobile phone to the network set up in the coffee shop differs from an IP subnet in case of the connection of the mobile phone to the network provided for free in the library. Such different IP subnets cause different IP addresses allocated to the mobile phone.
Due to the increasing use of handovers among selected IP traffic offload (SIPTO) schemes and techniques standardized in the 3rd Generation Partnership Project (3GPP), an IP address of a user equipment (UE) changes more frequently than before.
During data transmission and reception of a user equipment (UE) based on connection to a first network, if the UE is disconnected from the first network and is connected to another network, e.g., a second network, an IP address of the UE changes. The change of the IP address of the UE interrupts data transmission and reception. For example, if the UE is connected to a network using a transmission control protocol (TCP) and then is disconnected from the network, the connection is released. Since the connection is released, the UE needs to newly set up connection to the network. In another example, if the UE is connected to a network using a user datagram protocol (UDP) and then is disconnected from the network, the UE stops data transmission and reception until receiving a notification regarding a change of the IP address. If the UE has been using a voice over IP (VoIP) call through the connected network, the VoIP call is also stopped.
As such, the change of the IP address of the UE may stop data transmission and reception. To solve the problem, various methods have been used.
In one of those methods, the UE, even when moving, has a fixed IP address using a mobile IP or a general packet radio service (GPRS) tunneling protocol (GTP).
FIG. 1 illustrates a network using a mobile IP or a GTP.
If a user equipment (UE) 101 uses the mobile IP or the GTP, the UE 101 is connected to a packet data network gateway (PGW) or home agent (HA) 107, which is an IP gateway, before being connected to Internet 105 through a radio access network (RAN) 103. The UE 101 is connected to a web server 109 through the PGW or HA 107 and then through the Internet 105 (path 1, 113).
When using the mobile IP or the GTP, the UE 101 may have a unique IP address. Although the UE does not experience a change of the IP address due to the unique IP address, for the unique IP address of the UE, the PGW or HA has to be installed. The installation of the PGW or HA causes extra capital expenditure (CAPEX) and operating expenditure (OPEX), and so forth.
In addition, latency also increases because the UE is connected to the server through the PGW or HA.
Another problem of the mobile IP or the GTP is that the mobile IP or the GTP is not available in all networks. For example, if the UE is connected to a Wireless Fidelity (WiFi) network 111 installed at home or work (path 2, 115), the mobility of the UE may not be supported because of absence of the PGW or the HA. Herein, the mobility of the UE means that the UE, even when moving, may transmit and receive data without disconnection of an IP session.
To solve the aforementioned problem occurring in the use of the mobile IP or the GTP, a mobile IP route optimization (MIP RO) method has been proposed. The MIP RO method transmits and receives data without passing through the PGW or the HA, in spite of using the fixed IP address.
FIG. 2 illustrates the MIP RO method.
For mobile IP route optimization, the UE 101 transmits data directly to the web server 109 through the RAN 103 and the Internet 105 (path 3, 201), instead of transmitting the data through the PGW or the HA 107.
However, the MIP RO method also has some problems described below.
The MIP RO method is applicable only to the mobile IP. That is, the MIP RO method is not applicable when the GTP is used.
Moreover, a data transmission path of the UE 101 does not pass through the HA, but the MIP RO method still needs the HA.
For data transmission and reception to and from the web server 109, the UE 101 needs a separate setup procedure. More specifically, the UE 101 requires twice round-trip signaling (e.g., signaling with a domain name system (DNS) for an inquiry into a domain name of the web server) to set up a direct data transmission path for data transmission and reception to and from the web server 109. The separate setup procedure causes existence of setup latency.
A multi-path transmission control protocol (MPTCP) has been proposed as another method for supporting the mobility of the UE. An existing TCP uses a single path for data transmission and reception, whereas the MPTCP uses multiple paths. By using the multiple paths, even when one path is disconnected, the UE may transmit and receive data seamlessly with another path.
The MPTCP, however, has problems as described below.
The MPTCP is effective only when the TCP is used. That is, application of the MPTCP is not possible for other communication protocols, e.g., a UDP-based real-time transport protocol (RTP), a VoIP, quick UDP Internet connection (QUIC), a stream control transmission protocol (SCTP), etc.
The MPTCP may fail due to interference of a middle box existing on the network. The MPTCP uses a new TCP option (an option that is not supported by the existing TCP), and middle boxes such as a fire wall and network address translators (NATs) interrupt the new TCP option. Some middle boxes may not recognize the new TCP option and thus may give up the new TCP option or all data packets transmitted based on the new TCP option. Some other middle boxes may modify data transmitted based on the new TCP option. A correct operation of a middle box depends on an implementer and arrangement of the middle box, and thus is not actually known.
As a result, the MPTCP is not a fundamental solution for supporting the mobility of the UE, either.